Boris Johnson accused today of reneging on two key pledges - to stop the spread of "inappropriate" tower blocks and to preserve small shops.

It follows a letter of support from one of the Mayor's most senior aides for a 31-storey skyscraper that would result in the demolition of a popular east London market.

The building is part of a proposed £75million redevelopment of Queens Market in Upton Park, close to West Ham United's stadium.

The market, home to dozens of traders, would be replaced by a new facility.

Developer St Modwen submitted plans to Newham council on 1 May, the day Mr Johnson deposed Ken Livingstone as Mayor.

Campaigners had hoped the Tory's manifesto pledge to accept applications for skyscrapers only in existing "clusters", such as the City and Docklands, meant the proposals would be blocked.

But in a letter to the council, deputy mayor Ian Clement, who is handling the application for the Greater London Authority, said the scheme would be acceptable if the design quality of the tower "could be further demonstrated".

The letter, written on 27 June asked for some other minor changes but did not object in principle to the height of the tower or the destruction of the market.

Saif Osmani of the Friends of Queens Market said he was upset at the Mayor's approach: "The proposal is an uninspiring, high-rise development, out of character with local buildings which average two to three floors, mainly traditional Victorian terraced houses.

"It is out of context, will increase congestion in an already heavily congested area and will put over 100 local traders out of their shops, up to 80 per cent of whom are from ethnic minorities and already suffering poorer health and shorter life expectancy than national and London-wide averages.

"For these people Queens Market is a lifeline and a means to enter into work."

He said St Modwen has given assurances that it would work with tenants in the small shops to ensure sustainable rent levels but he claimed the company was now demanding a 100 per cent rent increase from one trader and one of over 40 per cent from another.

"This flies in the face of the reassurances given by the council and St Modwen that the market will survive the redevelopment," added Mr Osmani. In a letter to the Mayor, he said: "You have previously said tower blocks must fit into the 'local context' and will not be allowed in inappropriate locations.

"You criticised the previous mayor's love affair with high-rise buildings, which you said were 'wrecking London's skyline'. You have also pledged to protect local shops and independent traders. We look to you now not to go back on your word."

In his election manifesto, Mr Johnson signalled a change in planning policy from his predecessor, saying skyscrapers would have to be supported locally.

One proposal, the "Penny Whistle" tower in Ealing, has been scaled back from 40 to 24 storeys to comply with the priorities of the new regime. Last week the Mayor unveiled proposals requiring "affordable shops" to be included in any major new retail development.

The St Modwen application will be considered by Newham planning committee next month. The company was not available for comment.